Multi-currency: when should I use a percentage cap instead of a fixed minimum price?

A Minimum final price rule is published in your store's base currency. It only evaluates when checkout runs in that currency; orders in other currencies pass without that protection.
A Maximum discount percentage rule is relative, so the same cap applies no matter which currency the shopper checks out in.
Recommendation:

• Single-currency catalog → either mode works; use a fixed floor when the policy is about an absolute price (e.g. MAP policies).
• Multi-currency or multi-market catalog → use a percentage cap for reliable protection everywhere.